1. Field of the Invention
This invention relates to a cutting plant for cutting blanks out of a starting strip consisting particularly of a prepreg which is covered with facing film on one side or both sides, which plant comprises a cutting deck, which has a top surface to which a vacuum can be applied, a cutting carriage which is movable over said top surface and is provided with a cutting tool that is adjustable to cut to a defined depth and which preferably vibrates at an ultrasonic frequency, a dispenser for rotatably mounting a supply roll of said starting strip to be dispensed onto said top surface and a take-up device for rotatably mounting a take-up roll.
2. Description of the Prior Art
In the technology of fiber-reinforced plastics the term prepreg is used to describe a preimpregnated fibrous material which has been impregnated with a reactive resin composition in a predetermined proportion and can be cured under the action of heat without an application of pressure and without a need for further additives. That starting material is prefabricated as a strip which is covered by a facing film on one side or both sides and can be sound up to form a roll and can subsequently be processed in a suitable cutting plant, in which the desired blanks are cut out of the strip along a contour line which has been designed in consideration of the desired final product. In order to minimize waste, the several blanks should constitute a pattern, described as a nest, in which they are as close to each other as possible. In order to cut such blanks from the strip in the previous practice, the strip, which constitutes a supply roll in a dispenser at the receiving end of the cutting deck, is withdrawn by hand or by a gripper from the supply roll and is pulled over the top surface of the cutting deck. Thereafter the cutting unit cuts into the portion of the strip which lies on the top surface of the cutting deck and in accordance with a program cuts the blanks out of the piece of material which lies on the top surface of the cutting deck, which is described as a vacuum deck because the material is retained on the deck by a vacuum applied to its top surface. After the cutting operation the blanks are removed from the deck by hand and the waste is discarded before another length of strip is withdrawn from the supply roll and placed on the cutting deck. For this reason each cutting operation is restricted to a predetermined piece of material, which has the same length as the deck, i.e., the nest can have only a limited length. Because this restricts the freedom in the design of the nest, the proportion of waste is large and the feeding and removal of material to and from the cutting deck and the sorting of the blanks and of the waste are time-consuming and involve a high expenditure of work. As known cutting plants which operate efficiently and are highly automated and in which cutters which vibrate at an ultrasonic frequency can be adjusted to cut to a certain depth, such as the cutters known from British Patent Specification 2,148,175, have proved most satisfactory, the need for a manual handling of the material adversely affects the entire production sequence to a considerable degree.
Published German Patent Application 3,340,651 discloses a cutting plant in which the top surface of a cutting deck is preceded and succeeded by respective rolls of strip material. But said rolls of strip material are freely rotatably mounted and the strip which extends on the top surface of the cutting deck between said rolls must be pulled by the movable cutting carriage, which carries grippers, so that the material can be unwound and taken up. That arrangement will not permit the handling of the strip and the separation into blanks and waste to be effected with a higher efficiency.
It has also been proposed to accelerate the sequence of operations by the provision of a cutting deck which consists of a pallet deck so that two or more pallets may be used and the waste may be separated from the blanks at a location which is remote from the cutting deck and cutting and sorting operations can be performed on the same time. But that faster processing involves a higher structural expenditure for the pallet deck and even the use of the pallet deck does not permit a nest to be designed which is longer than the pallet. Similar remarks are applicable to known conveyor decks, in which the top surface is constituted by a conveying belt rather then by replaceable pallets. In that case the blanks and the waste are conveyed to a collecting container when the cutting operation proper has been performed and the blanks and waste are separated outside the cutting station. In that case too the length of the nest is substantially limited by the length of the top surface which is constituted by the conveying belt and the use of a conveying belt gives rise to difficulties in the cutting operation. Moreover, in plants comprising a pallet deck and a conveyor deck the application of a vacuum to the top surface of the deck and, as a result, the retention of the strip as it is cut, are unsatisfactory.